1. Field of the Invention:
This invention relates to devices for conserving oxygen as utilized in supplemental oxygen therapy for human patients, particularly those receiving oxygen therapy via a tracheostomy tube assembly.
2. Description of the Prior Art:
Long term conventional oxygen therapy is commonly prescribed for patients who have compromised respiratory capabilities, often resulting from an acute infection or a chronic illness, such as emphysema. While these patients are capable of normal or nearly normal respirations, their oxygen exchange is not sufficient and it must be supplemented. Some pulmonary conditions have also required the use of a tracheostomy tube with oxygen supplied directly to the patient's trachea. The majority of the patients receiving supplemental oxygen, either through a nasal cannula or tracheostomy tube, utilize conventional oxygen therapy equipment which includes a pressurized oxygen tank with a regulator and an oxygen line endwardly connected to the nasal cannula, or tracheostomy tube. Sometimes a humidifying unit is also used with oxygen therapy equipment. These patients still breath the ambient air but are merely supplemented with additional oxygen. For patients having a chronic pulmonary problem, they must receive supplemental oxygen on a long term or permanent basis. There have been several disadvantages noted with the conventional long term management of oxygen therapy patients. Since the oxygen is supplied at a continuous flow rate, the patient is still administered oxygen during exhalation as well as inhalation. During exhalation, the oxygen supplied by the oxygen tank is expelled with the patient's exhaled air, thus wasting the oxygen. Therefore, more oxygen is dispensed from the oxygen tank than is actually used by the patient. This is not only a waste of money but refills of portable oxygen tanks are made much more often than would otherwise be necessary. Since oxygen is dispensed constantly, the nasal mucosa and other tissues of the patient can become dehydrated, and humidification of the oxygen is therefore sometimes necessary, which is also another added expense.
Another disadvantage of the traditional oxygen therapy equipment is the air exhaled by the patient must exceed the pressure of the dispensed oxygen through the tracheostomy tube in order to be expelled through the nose or mouth around the cannula, thus requiring the patient to exhale slightly more forcefully than normal to exhale against this pressure. For weak and debilitated patients this can actually be tiring over an extended period of time.
Conventional oxygen therapy equipment also does not compensate for the temperature of the dispensed oxygen, which at times can be disagreeably cold to the patient. If the temperature were consistently cold and administered over an extended period of time, the patient's temperature could conceivable be lowered, possibly compromising the patient's health, not to mention the patient's comfort.
There are several past art devices which function as oxygen conserving devices. One such device is the oxygen delivery apparatus patented by Tiep et al, U.S. Pat. No. 4,535,757. Tiep's device is available as an accessory attachment to existing oxygen equipment, and functions to conserve oxygen by temporarily restricting the flow of oxygen out the nasal cannula during exhalation, utilizing the pressure differentials between the oxygen flow and the patient's exhalations. This is accomplished by providing a narrow elongated chamber with a flexible diaphragm, wherein the diaphragm blocks the outlet ports of the nasal cannula during the last phase of inhalation. During exhalation, the patient's exhaled air fills the chamber and forces the diaphragm aside, allowing oxygen to mix with the exhaled air. Thus the flow of oxygen is temporarily directed into the chamber when the patient exhales instead of being dispensed out the nasal cannula, thus saving oxygen.
There are several disadvantages to the Tiep et al device, one being the fact that the patient is rebreathing his own exhalations and therefore the oxygen which is administered to the patient is diluted. By diluting the oxygen mixture which the patient is prescribed, he may not be receiving sufficient oxygen to be beneficial or therapeutic. The chamber of the Tiep device is also relatively small and retains a fixed volume of oxygen, which may be sufficient for sedentary patients. However, this fixed volume would not be of sufficient volume to compensate the patient during exertion when the demand for oxygen would be greater. Even during sedentary states, all people need to occasionally take in a large cleansing breath, which the Tiep device would not compensate for.
Another more significant disadvantage of the Tiep et al device in that the exhaled air forced into the chamber could carry potentially infectious germs which could accumulate within the chamber and create a source for respiratory infections. The patient's exhalations are warm and moist and help to create a favorable environment within the chamber for growing the microbes. Also, the moisture of the exhalations could condense and accumulate, causing blockage problems. Many patients on oxygen therapy are generally already in a medically compromised condition or they wouldn't be needing the supplemental oxygen, and respiratory infections are especially serious to these patients since it is their lungs which are generally debilitated. Infections which would be minor to healthy individuals can be potentially lethal to patients with pulmonary deficiencies.
Another oxygen conserving device, currently in the market place, is sold under the tradename of OXYMIZER PENDANT, marketed by Chad Therapeutic, Inc., 9445 De Soto Ave, Chatsworth, Calif. 91311. The OXYMIZER PENDANT includes a bladder or diaphragm housed within an annular housing which is connectable between the oxygen tank and a nasal cannula. The OXYMIZER PENDANT saves oxygen by creating pressure differentials between the force of the patient's exhalation and the dispensed oxygen. Pressure increases in the nasal cannula, tubing and bladder as the patient exhales, forcing the lower pressurized oxygen dispensed from the tank to back-up within the bladder instead of being expelled upon exhalation, and thus wasted. The disadvantage of this system also involves the dilution of the oxygen with the exhaled used air. This is most significant when the patient is under stress or physical exertion where the force of exhalation is much greater than during sedentary periods. During exertion, much more exhaled air is forced into the air lines and possibly into the bladder or reservoir, significantly reducing the overall amount of oxygen available to the patient. Since the patient would require much more oxygen during exertion, the reduction in oxygen due to the dilution factor could adversely affect the patient. Therefore, the pressure differentials under which the OXYMIZER PENDANT best functions, only exist within a narrow range of parameters with the patient presumably remaining sedentary and the pressure of the oxygen dispensed from the tank remaining lower than the pressure of the patient's exhalations. Any variations in these parameters and a significant amount of oxygen can be lost, thus reducing the savings.
More importantly, the OXYMIZER PENDANT also allows the introduction of exhaled air into the air line and possibly even into the storage bladder. The exhaled air, as previously mentioned, can carry microbes which could lead to infection, and could even cause chronic or recurrent respiratory problems for the patient. Moisture condensation from the exhalations could also prove a problem by accumulating and causing partial or complete blockage of the oxygen flow.
Additionally, the OXYMIZER PENDANT apparently has no structural arrangement which would allow it to be used for introducing oxygen into a tracheostomy tube or assembly, which is becoming an increasingly popular method of applying oxygen therapy.
There is therefore a need for an oxygen conserving device which prevents the potential introduction of infectious agents into the oxygen system and provides the patient with oxygen undiluted with carbon dioxide, and which can also be utilized with tracheostomy tube assemblies.